Polarizer filter(wide band)


eljo99

New Member
Dec 11, 2006
39
0
0
#1
Hi guys,

Dunno if its the rite places to post these..... i'm just curious abt 2 question:

1) What is a WIDE BAND circular polarizer?? as we know what does a circular polarizer did already.

2) Is there certain relationship between focal length and polarizer filter? i heard there is some relationship between focal length and ND filter, but not too sure abt it.

Can any kind soul point point to any link or explain?? maybe that had been discussed but i no see in recent posting anywhere.. ;p

thks for enlightening....:thumbsup:
 

daredevil123

Moderator
Staff member
Oct 25, 2005
21,636
59
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lil red dot
#2
Hi guys,

Dunno if its the rite places to post these..... i'm just curious abt 2 question:

1) What is a WIDE BAND circular polarizer?? as we know what does a circular polarizer did already.

2) Is there certain relationship between focal length and polarizer filter? i heard there is some relationship between focal length and ND filter, but not too sure abt it.

Can any kind soul point point to any link or explain?? maybe that had been discussed but i no see in recent posting anywhere.. ;p

thks for enlightening....:thumbsup:
I answer your questions in reverse:

2. There is no relationship. But if the focal length is too wide you will get uneven polarization when using CPL... This link explains uneven polarization. This pic shows what it looks like. So it is generally not a very good idea to use CPL with UWA lenses.

The amount of polarization in the sky is not constant. Polarization is at a maximum at an angle of 90 degrees to the sun, and goes to zero directly towards and away from the sun.

Therefore, when using a polarizing filter on a wide angle lens which can "see" many different parts of the sky at once, the effect of the polarizer is 'uneven' such that some parts of the sky are darker than others in the final image. Typically this appears as a dark band in a clear blue sky.

1. Wide band means the polarizing band is wider, meaning you can use it on wider lenses without uneven polarization. But on ultra wide angles, it will probably still give you uneven polarization... You need to read up on the specs of the specific filter to know what is the min focal length this CPL will work ok.
 

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